year

year the time taken by the earth to make one revolution around the sun. The length of the year depends on the manner of calculation. For ordinary purposes the important period is the tropical year (also called astronomical year, equinoctial year, or solar year) which is the time between successive spring or autumn equinoxes, or winter or summer solstices, roughly 365 days, 5 hours, 48 minutes, and 46 seconds in length. This period thus marks the regular cycle of the seasons.

The calendar year or civil year is the period of 365 days (or 366 days in leap years) starting from the first of January, used for reckoning time in ordinary affairs.

The word is recorded from Old English (in form gē(a)r) and is of Germanic origin; it comes from an Indo-European root shared by Greek hōra ‘season’.
a year and a day a legal period constituting a term for certain purposes, in order to ensure the completion of a full year.
year of grace year — ad, suggested by medieval Latin anno gratiae, used by chroniclers to indicate the year as reckoned from the birth of Christ. Year of Our Lord is year — ad, as reckoned from the birth of Christ; anno domini.
Year 2000 problem (also called Y2K) another name for the Millennium bug.
year's mind the anniversary of a person's death or burial, as an occasion for special prayers; a Requiem Mass held on such an anniversary; the term is recorded from the 11th century.

See also a cherry year, a merry year, donkeys' years at donkey, locust years, next year in Jerusalem.